This invention relates to a method of and apparatus for the continuous manufacture of metal profile members of open or closed construction, especially steel profile members, from a continuous band or strip of metal.
Metal profile members of closed or open construction having a wide variety of different cross-sectional configurations are commonly produced in a continuous manufacturing process involving hot- or cold-rolling.
Hot rolling is used for the manufacture in large batches of open profile members having simple cross-sectional configurations. However, hot-rolling is not suitable for the production of profile members having complex cross-sectional configurations or in certain instances where there is an extreme relation between the dimension and thickness of a profile member. Extrusion processes permit the production of complex open and closed metal profile members within certain narrow limitations. However, such extrusion processes are generally very costly.
In addition to the above-mentioned hot deformation processes which require the initial materials, e.g., ingots, billots, stampings, etc., to be uniformly heated to a high temperature to permit deformation, a substantial amount of rod-shaped profile members are produced by cold deformation at room temperature from sheet and strip metal by means of profile rolling, camphoring and drawing. Profile members obtained by cold deformation generally are limited to those having cross-sections of substantially uniform wall thickness except in those areas where bending occurs during the cold deformation operation. Furthermore, cold-shaping requires for leverage purposes a minimum width of the material depending upon the thickness and the quality of the material and upon the bending radii of the material.
A wide variety of hot- and cold-shaping methods are used for the production of tube sections. A common factor in all of these processes, however, is that as a general rule the wall thickness must be constant over the entire cross-section. Only in special instances is it possible by utilizing more expensive extrusion processes to produce members having tubular cross-sections with differences of wall thickness, and in these instances this is possible only within certain limits.
There has long been an extensive need for rod-like profile members, especially steel profile members having open or closed cross-sectional configurations, which cannot be produced, for either technical or economic reasons, by any of the above-mentioned known methods. The profile members which are produced are relatively thin walled, and the main part of the cross-section of such profile members is of uniform thickness. Only in certain parts of the cross-section is it possible to reduce or increase the thickness by shifting the material of the profile member laterally as it is being produced to provide local reductions or accumulations of material. With respect to the formation of local accumulations of material within the cross-section, attempts have been directed to develop mainly cold processes for producing profile members having acute angled outer radii. Such processes require the use of hot-rolled bands of metal material having one or more beads therein which are shaped by cold processes (see Journal of the German Research Body for Sheet Metal Working and Surface Treatment (Regd. Assocn.) and Mitteilungen Der Deutschen Forschungsgesellschaft f/u/ r Boechberarbeitung und Oberfl/a/ chenbehandlung e. V., Vol. 19, 1968, No. 13, pp. 209-221). This technology has, however, been superseded by modern hot-rolling processes since it is not feasible to provide a substantial number of different types of bead-containing metal band material, particularly when only small batches of metal profile members are being produced.
Attempts have also been made to partially heat cold-formed products in order to alter certain parts of the material, especially the bent edges, the thickness of the material remaining unaltered.
Also, it is known to improve cold-shaping by elevating the process temperature. Various heat sources have been used which heat not only the band material but also the shaping tools. However, hot-shaping temperatures in excess of 800.degree. C. have not been attempted, the object having been merely to facilitate the shaping of materials which are either difficult or impossible to deform at room temperature. These methods are not significant industrially (B/a/ nder-Bleche-Rohre, August 1967, No. 7, pp. 458-469).